1. Field of the Invention
The present invention relates to the preparation of chlorophenols, and, more especially, to the preparation of chlorophenols from chlorocyclohexanones.
2. Description of the Prior Art
Chlorocyclohexanone-to-chlorophenol type processes are generically known to this art.
The earliest known process, for example, comprises heating 2,3,5,6-tetrachlorocyclohexanone at a temperature of 260.degree.-270.degree. C. to prepare 2,6-dichlorophenol [Acta Chemica Scandinavia, 4, 200-4 (1950)]. However, only very low yields are realized thereby.
Another process is described in French Patent Application No. 72/1,083, published under No. 2,125,280. Same comprises heating 2,2,6,6-tetrachlorocyclohexanone or 2,2,6-trichlorocyclohexanone at a temperature between 100.degree. and 250.degree. C., in the presence of an amine, an amide, a urea or one of their salts with acids, in order to prepare 2,6-dichlorophenol and ortho-chlorophenol, respectively. It is apparent from reading the examples of the aforesaid patent application, and from confirming independent testing, that the best yields are obtained at a temperature of about 200.degree. C.
Although this second process makes it possible to improve the yield, on the one hand, and to substantially lower the reaction temperature, on the other hand, compared with the first process, it is thus apparent that serious need exists in this art for a process which could be carried out at lower temperatures and at a faster rate than those of the prior art, while suffering no diminution in yields.
See also Beringer et al, JACS, 71, pp. 2633-2635 (1953); Chemical Abstracts, 89, No. 15, p. 559, item 129172z (1978); U.S. Pat. Nos. 3,532,740 and 3,660,505; Pudovik et al, Izv. Akad. Nauk SSSR, Ser. Khim., (7), 1660-1 (1978); West German Pat. No. 64,426; Dutch published application No. 75 09 917; and published French applications Nos. 2,002,799, 2,079,575 and 2,285,355.